The present invention relates generally to earth working agricultural implements and more specifically relates to trip mechanisms which enable a tool support and earth working tool to rotate as obstructions are encountered to avoid structural damage.
Earth working implements having safety trip mechanisms are old in the art. These mechanisms include those which automatically reset after being tripped and those which do not automatically reset. Trip mechanisms not designed to reset automatically include both toggle link and roller pin types. For examples of these mechanisms, see U.S. Pat. Nos. 2,860,564 and 2,850,957, respectively.
Toggle link trip mechanisms are held in an uncollapsed position by springs and resist tripping by tolerating compressive forces through the toggle links. The links are designed to collapse about their common joint and permit rotation of the tool supporting standard after the compressive forces have exceeded a threshold value sufficient to overcome the spring force. These trip mechanisms are not consistently responsive to defined force levels due to variations in manufacturing tolerances and material characteristics. Therefore, the threshold force required to trip the mechanism often varies.
Roller trip mechanisms typically provide a roller pin carried by the standard which is tripped from a spring loaded notched or cam surface on the link or frame. The trip mechanisms are designed to trip as a predetermined force is applied. However, as the interacting pin and notched surfaces become flattened or worn, forces different than from the forces for which the trip mechanism is designed often cause the pin to release from the notched or cam surface. Further, threshold forces required to trip the mechanisms often vary from the designed threshold force due to defects in manufacturing, inconsistencies in materials used, and poor maintenance and lubrication habits of owner-operators.